Soap mainly removes partcles like grease or dirt which is unremovable by water.
Soaps for cleansing are obtained by treating vegetable or animal oils and fats with a strongly alkaline solution.
Soaps are sodium or potassium fatty acids salts
The organic part of a natural soap is a negatively-charged, polar molecule. Its hydrophilic (water-loving) carboxylate group (-CO2) interacts with water molecules via ion-dipole interactions and hydrogen bonding.
Some soaps which acts as lubricants makes two moving surfaces reduce the friction between them, improving efficiency and reducing wear. It may also have the function of dissolving or transporting foreign particles and of distributing heat.
Soaps also helps to remove dirt particles which are irritable to our eyes or may be harmful to our body.